This specification relates to digital data processing, and in particular, to computer-implemented search services.
Internet search engines provide information about Internet accessible resources (e.g., web pages, images, documents, multimedia content) that are responsive to a user's search query by returning a set of search results in response to the search query. A search result includes, for example, a Uniform Resource Locator (URL) and a snippet of information for resources responsive to a query. The search results can be ranked (e.g., in an order) according to scores assigned to the search results by a scoring function. The search results can be presented in a search results web page. In some situations, advertisements that are responsive to the user's search query can also be presented in the search results web page.